二进制中1的个数： https://www.nowcoder.com/practice/8ee967e43c2c4ec193b040ea7fbb10b8?
class Solution {
    public:
    int NumberOf1(int n) {
        int count = 0;
        while (n) 
        {
            n &= (n - 1); //可以避免无效检测
            count++;
        }
        return count;
    }
};